Instruction by a teacher of students assembled in a classroom is an effective method of teaching, since a student in a classroom can ask questions of the teacher and receive an immediate answer to clarify points of the lesson being taught which the student does not understand. In addition, the teacher can pose questions to students in the classroom and receive immediate replies to maintain the attentiveness of the students and to verify that the students are comprehending the lesson being taught.
However, it is often necessary to teach students who cannot be brought together in a classroom with a teacher. For example, it may be necessary to teach students who are hospitalized or who for some other reason cannot attend a classroom lecture. It may also be desired to provide instruction in a continuing-education program or employee-training program to persons no longer in school who live or work at widely dispersed sites and for whom it would be impractical to bring together in a classroom for instruction.
Various schemes involving televised or video-taped lectures have been tried for teaching students at sites remote from a teacher. However, no altogether satisfactory method has heretofore been available for teaching students located at sites remote from each other and the teacher.
One approach for teaching students in remote sites involves providing a direct television link between each student site and the teacher in parallel with a telephone link between the student sites and the teacher. In this way the lecture of the teacher can be transmitted "live" to each of the students and the students can ask questions of the teacher over the telephone link. However, a direct television link to a remote site is extremely expensive and consequently live broadcasts of a lecture with provision for student response by telephone is generally impractical for economic reasons, particularly when more than a few student sites are involved.
An article by D. Scott published in the February 1982 issue of Popular Science discloses a micro-processor-based audio-visual teaching system for linking students at widely scattered study centers and a teacher at a university. Terminal equipment for each study center consists of a microprocessor unit, a television set, two telephone lines and a stereo cassette recorder. Prerecorded lessons can be played on the stereo cassette recorder. One of the telephone lines is for audio communications and the other telephone line is for communicating visual information. The teaching system of the Scott article provides for talk-back and write-back from every terminal. Write-back is accomplished by means of a light pen. The system uses internal programs that can be taped, transmitted live or a mixture of the two. A teacher can make his or her own taped lessons by recording illustrative material with a television camera, making drawings on a graphics tablet, or entering typed information on a keyboard. The picture elements thus entered can be arranged and scaled on a video monitor to suit the teacher and then transferred to a stereo cassette tape. According to the article, the tape can be used by individual machines or sent over phone lines.
The audio-visual teaching system disclosed in the Scott article has a number of significant drawbacks. For example, conventional stereo cassette tapes have limited data storage capacity so that only a relatively limited set of images can be stored on the tape.